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I can't find the answer for this question anywhere on the internet. My friend and I made butterfly pea jelly with gelatin and we used the same recipe. Mine came out fine with blue color of butterfly pea flowers but my friend's changed its color to dark purple after adding gelatin.

My friend lives in Asia and me in Europe, so I think our source of ingredients (gelatin, water, flowers) is different. Plus, our method is slightly different. My friend heated the tea to melt gelatin while I stired gelatin over hot water to melt it and then mixed it up with the tea.

My friend is pretty sure it was because of gelatin because she didn't have this problem when trying with agar agar. Although I know butterfly pea tea is very sensitive to pH, I just can't find a good explanation for this. Is it really because of gelatin?

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From the Gelatin Manufacturer's Institute of America "Gelatin Handbook": https://nitta-gelatin.com/wp-content/uploads/2018/02/GMIA_Gelatin-Handbook.pdf

Gelatin in solution is amphoteric, capable of acting either as an acid or as a base. In acidic solutions gelatin is positively charged and migrates as a cation in an electric field. In alkaline solutions gelatin is negatively charged and migrates as an anion. The pH of the intermediate point, where the net charge is zero and no movement occurs, is known as the Isoelectric Point (IEP) (28). Type A gelatin has a broad isoelectric range between pH 7 and 9. Type B has a narrower isoelectric range between pH 4.7 and 5.4 (29-32)

Emphasis mine.

So it does not seem impossible that your various brands of gelatin were produced by different processes and that one would be more acidic than the other. If you had a Type A gelatin and your friend a low-pH Type B, that would explain what you were seeing.

I do not think your method of heating had any effect.

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  • Thank you very much for your answer. I'm wondering if one type of gelatin is better than the other?
    – Sean
    Commented Feb 14, 2021 at 13:42
  • According to the same document, both types of gelatin can be produced to the same range of bloom strengths. I'm not sure what else you might mean by "better".
    – Alex Reinking
    Commented Feb 14, 2021 at 18:08
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TIL about butterfly pea tea

In general, different ingredients (even same ingredients from different part of the world) will result in slightly different end product.

As far as I understand, the ph of the water will change the colour of the resulting tea from blue to purple; you should experiment by adding a little bit of acid (lemon juice) to change the acidity of the water.

See https://spoonuniversity.com/lifestyle/what-is-butterfly-pea-flower-tea-hint-it-changes-color

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  • This doesn't sound like an explanation. The water's effect was already visible when brewing (a blue tea) and the color changed when gelatine was added. Presumably, the friend uses water from the same source to both brew tea and soak gelatine.
    – rumtscho ♦
    Commented Feb 14, 2021 at 10:13

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